The disclosed technology relates to zinc-free lubricants for internal combustion engines, which contain metal-free additives to provide cleanliness to the lubricant as well as zinc-free phosphorus anti-wear additives.
Lubrication of internal combustion engines has been a practice for many decades, yet continual improvement in lubricant technology is ongoing as new engines and new standards have been developed. Formulations directed to spark ignition engines and compression ignition engines, for instance, must address limits placed on sulfated ash, phosphorus, and sulfur content (“SAPS”), and restrictions in these components often lead to upper limits on the amount of metal-containing additives that can be included in the lubricant. Reduction in metal containing additives is necessary to reduce the impact of metal ash on exhaust aftertreatment devices and to reduce the emission of particulate matter.
Chief among these metal-containing additives are zinc dialkyldithiophosphates (ZDDP) for wear and oxidation protection and overbased metal detergents for cleanliness and acid control. ZDDP has been the industry standard for reducing valve train wear, protecting against liner wear, and reducing oxidation leading to corrosive wear. However the zinc contributes to an increase in sulfated ash in the lubricating oil and the phosphorus causes inactivation of oxidation catalysts used in exhaust after-treatment devices.
U.S. Patent Publication 2011-0297122 discloses a low ash, zinc-free consumable lubricant composition for use in an internal combustion engine equipped with a pilot ignition system.
U.S. Patent Publication 2007-0111905 discloses lubricant compositions for heavy duty diesel engines which are free of zinc dialkyldithiophosphates. These compositions contain metal-containing detergents, preferably calcium sulfonate and/or calcium phenate detergents.
U.S. Patent Publication 2005-0043191 discloses a substantially zinc and phosphorus free lubricating oil which contains an additive system containing metal detergents, at least one borated ashless dispersant, at least an amine anti-oxidant and a tri-nuclear molybdenum compound. The lubricant contains a minimum of 120 ppm boron and a minimum of 80 ppm molybdenum.
U.S. Patent Publication 2005-0026792 discloses a lubricating oil composition with very low phosphorus content, and having long life as evidenced by a reduction in viscosity increase, oxidation and nitration, comprises a major amount of a base oil of lubricating viscosity and a minor amount of a mixer of neutral and overbased metallic detergents, at least a zinc di-alkyl di-thiocarbamate anti-wear additive and at least a di-hydrocarboxylthiocarbamoyl.
U.S. Patent Publication 2005-0137096 discloses an engine lubricant that is substantially free of zinc and phosphorus contains an anti-wear additive comprising borated 1,2-epoxy mixed polybutenes having an average carbon number in the range of C20 to C120.
WO publication 2014-193543 discloses lubricating compositions for compression ignition internal combustion engines containing oxyalkylated hydrocarbyl phenols, especially to aid in soot and deposit control. The examples describe lubricant compositions containing both zinc dialkyldithiophosphates as well as overbased calcium detergents.
The disclosed technology provides a lubricant composition for an internal combustion engine wear protection, deposit control, and improved acid control.